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11 pages, 764 KiB

Open AccessArticle

Fused Microknot Optical Resonators in Folded Photonic Tapers for in-Liquid Durable Sensing

by Alexandra Logvinova, Shir Shahal, Moti Fridman and Yoav Linzon

Sensors 2018, 18(5), 1352; https://doi.org/10.3390/s18051352 - 26 Apr 2018

Cited by 8 | Viewed by 3373

Abstract

Optical microknot fibers (OMFs) serve as localized devices, where photonic resonances (PRs) enable self-interfering elements sensitive to their environment. However, typical fragility and drifting of the knot severely limit the performance and durability of microknots as sensors in aqueous settings. Herein we present [...] Read more.

Optical microknot fibers (OMFs) serve as localized devices, where photonic resonances (PRs) enable self-interfering elements sensitive to their environment. However, typical fragility and drifting of the knot severely limit the performance and durability of microknots as sensors in aqueous settings. Herein we present the fabrication, electrical fusing, preparation, and persistent detection of volatile liquids in multiple wetting–dewetting cycles of volatile compounds and quantify the persistent phase shifts with a simple model relating to the ambient liquid, enabling durable in-liquid sensing employing OMF PRs. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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9 pages, 5058 KiB

Open AccessArticle

Discrimination of Temperature and Strain in Brillouin Optical Time Domain Analysis Using a Multicore Optical Fiber

by Mohamed A. S. Zaghloul, Mohan Wang, Giovanni Milione, Ming-Jun Li, Shenping Li, Yue-Kai Huang, Ting Wang and Kevin P. Chen

Sensors 2018, 18(4), 1176; https://doi.org/10.3390/s18041176 - 12 Apr 2018

Cited by 26 | Viewed by 4978

Abstract

Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a [...] Read more.

Brillouin optical time domain analysis is the sensing of temperature and strain changes along an optical fiber by measuring the frequency shift changes of Brillouin backscattering. Because frequency shift changes are a linear combination of temperature and strain changes, their discrimination is a challenge. Here, a multicore optical fiber that has two cores is fabricated. The differences between the cores’ temperature and strain coefficients are such that temperature (strain) changes can be discriminated with error amplification factors of 4.57 °C/MHz (69.11

μ ϵ

/MHz), which is 2.63 (3.67) times lower than previously demonstrated. As proof of principle, using the multicore optical fiber and a commercial Brillouin optical time domain analyzer, the temperature (strain) changes of a thermally expanding metal cylinder are discriminated with an error of 0.24% (3.7%). Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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15 pages, 44588 KiB

Open AccessArticle

Soil Water Measurement Using Actively Heated Fiber Optics at Field Scale

by Duminda N. Vidana Gamage, Asim Biswas, Ian B. Strachan and Viacheslav I. Adamchuk

Sensors 2018, 18(4), 1116; https://doi.org/10.3390/s18041116 - 6 Apr 2018

Cited by 24 | Viewed by 5770

Abstract

Several studies have demonstrated the potential of actively heated fiber optics (AHFO) to measure soil water content (SWC) at high spatial and temporal resolutions. This study tested the feasibility of the AHFO technique to measure soil water in the surface soil of a [...] Read more.

Several studies have demonstrated the potential of actively heated fiber optics (AHFO) to measure soil water content (SWC) at high spatial and temporal resolutions. This study tested the feasibility of the AHFO technique to measure soil water in the surface soil of a crop grown field over a growing season using an in-situ calibration approach. Heat pulses of five minutes duration were applied at a rate of 7.28 W m⁻¹ along eighteen fiber optic cable transects installed at three depths (0.05, 0.10 and 0.20 m) at six-hour intervals. Cumulative temperature increase (T_cum) during heat pulses was calculated at locations along the cable. While predicting commercial sensor measurements, the AHFO showed root mean square errors (RMSE) of 2.8, 3.7 and 3.7% for 0.05, 0.10 and 0.20 m depths, respectively. Further, the coefficients of determination (R²) for depth specific relationships were 0.87 (0.05 m depth), 0.46 (0.10 m depth), 0.86 (0.20 m depth) and 0.66 (all depths combined). This study showed a great potential of the AHFO technique to measure soil water at high spatial resolutions (<1 m) and to monitor soil water dynamics of surface soil in a crop grown field over a cropping season with a reasonable compromise between accuracy and practicality. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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22 pages, 85745 KiB

Open AccessArticle

Embedded Distributed Optical Fiber Sensors in Reinforced Concrete Structures—A Case Study

by António Barrias, Joan R. Casas and Sergi Villalba

Sensors 2018, 18(4), 980; https://doi.org/10.3390/s18040980 - 26 Mar 2018

Cited by 110 | Viewed by 10049

Abstract

When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading [...] Read more.

When using distributed optical fiber sensors (DOFS) on reinforced concrete structures, a compromise must be achieved between the protection requirements and robustness of the sensor deployment and the accuracy of the measurements both in the uncracked and cracked stages and under loading, unloading and reloading processes. With this in mind the authors have carried out an experiment where polyimide-coated DOFS were installed on two concrete beams, both embedded in the rebar elements and also bonded to the concrete surface. The specimens were subjected to a three-point load test where after cracking, they are unloaded and reloaded again to assess the capability of the sensor when applied to a real loading scenarios in concrete structures. Rayleigh Optical Frequency Domain Reflectometry (OFDR) was used as the most suitable technique for crack detection in reinforced concrete elements. To verify the reliability and accuracy of the DOFS measurements, additional strain gauges were also installed at three locations along the rebar. The results show the feasibility of using a thin coated polyimide DOFS directly bonded on the reinforcing bar without the need of indention or mechanization. A proposal for a Spectral Shift Quality (SSQ) threshold is also obtained and proposed for future works when using polyimide-coated DOFS bonded to rebars with cyanoacrylate adhesive. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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7 pages, 1234 KiB

Open AccessArticle

Two-Dimensional Layered Nanomaterial-Based One-Dimensional Photonic Crystal Refractive Index Sensor

by Jitendra B. Maurya, Alexandre François and Yogendra K. Prajapati

Sensors 2018, 18(3), 857; https://doi.org/10.3390/s18030857 - 14 Mar 2018

Cited by 49 | Viewed by 7584

Abstract

One-dimensional photonic crystal (1DPC) sensors have emerged as contenders for traditional surface plasmon resonance sensors, owing to their potential for the detection of bigger molecules and particles due to their higher interaction volume in the sensing medium. Two-dimensional layered nanomaterials, most notably graphene [...] Read more.

One-dimensional photonic crystal (1DPC) sensors have emerged as contenders for traditional surface plasmon resonance sensors, owing to their potential for the detection of bigger molecules and particles due to their higher interaction volume in the sensing medium. Two-dimensional layered nanomaterials, most notably graphene and dichalcogenides (e.g., MoS₂, MoSe₂, WS₂, and WSe₂), have shown higher refractive index sensitivity because of their absorption as well as adsorption property. The proposed configuration of 1DPC presented consists of alternate layers of the aforementioned nanomaterials and silicon. The performance parameters, namely the sensitivity, resolution, quality factor, and the evanescent field penetration depth, are calculated and compared with 1DPC having poly methyl methacrylate (PMMA) in place of silicon. Increased shift in resonance angle and quality factor are observed by replacing PMMA with silicon, but at the cost of decreased resolution. Further, our results show that although the sensitivity and quality factor of the 1DPC sensor is less than that of the conventional surface plasmon resonance sensor (SPR) with a gold thin film, it has much higher resolution and penetration depth to make it suitable for large molecules. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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17 pages, 3168 KiB

Open AccessArticle

Detection of Internal Metal Loss in Steel Pipes and Storage Tanks via Magnetic-Based Fiber Optic Sensor

by Safieh Almahmoud, Oleg Shiryayev, Nader Vahdati and Paul Rostron

Sensors 2018, 18(3), 815; https://doi.org/10.3390/s18030815 - 8 Mar 2018

Cited by 14 | Viewed by 9499

Abstract

A monitoring solution was developed for detection of material loss in metals such as carbon steel using the force generated by permanent magnets in addition to the optical strain sensing technology. The working principle of the sensing system is related to the change [...] Read more.

A monitoring solution was developed for detection of material loss in metals such as carbon steel using the force generated by permanent magnets in addition to the optical strain sensing technology. The working principle of the sensing system is related to the change in thickness of a steel plate, which typically occurs due to corrosion. As thickness decreases, the magnetostatic force between the magnet and the steel structure also decreases. This, in turn, affects the strain measured using the optical fiber. The sensor prototype was designed and built after verifying its sensitivity using a numerical model. The prototype was tested on steel plates of different thicknesses to establish the relationship between the metal thickness and measured strain. The results of experiments and numerical models demonstrate a strong relationship between the metal thickness and the measured strain values. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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21 pages, 9155 KiB

Open AccessArticle

Modeling and Analysis of a Combined Stress-Vibration Fiber Bragg Grating Sensor

by Kun Yao, Qijing Lin, Zhuangde Jiang, Na Zhao, Bian Tian, Peng Shi and Gang-Ding Peng

Sensors 2018, 18(3), 743; https://doi.org/10.3390/s18030743 - 1 Mar 2018

Cited by 22 | Viewed by 5837

Abstract

A combined stress-vibration sensor was developed to measure stress and vibration simultaneously based on fiber Bragg grating (FBG) technology. The sensor is composed of two FBGs and a stainless steel plate with a special design. The two FBGs sense vibration and stress and [...] Read more.

A combined stress-vibration sensor was developed to measure stress and vibration simultaneously based on fiber Bragg grating (FBG) technology. The sensor is composed of two FBGs and a stainless steel plate with a special design. The two FBGs sense vibration and stress and the sensor can realize temperature compensation by itself. The stainless steel plate can significantly increase sensitivity of vibration measurement. Theoretical analysis and Finite Element Method (FEM) were used to analyze the sensor’s working mechanism. As demonstrated with analysis, the obtained sensor has working range of 0–6000 Hz for vibration sensing and 0–100 MPa for stress sensing, respectively. The corresponding sensitivity for vibration is 0.46 pm/g and the resulted stress sensitivity is 5.94 pm/MPa, while the nonlinearity error for vibration and stress measurement is 0.77% and 1.02%, respectively. Compared to general FBGs, the vibration sensitivity of this sensor is 26.2 times higher. Therefore, the developed sensor can be used to concurrently detect vibration and stress. As this sensor has height of 1 mm and weight of 1.15 g, it is beneficial for minimization and integration. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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10 pages, 1770 KiB

Open AccessArticle

Fiber-Optic Pyrometer with Optically Powered Switch for Temperature Measurements

by Carmen Vázquez, Sandra Pérez-Prieto, Juan D. López-Cardona, Alberto Tapetado, Enrique Blanco, Jorge Moreno-López, David S. Montero and Pedro C. Lallana

Sensors 2018, 18(2), 483; https://doi.org/10.3390/s18020483 - 6 Feb 2018

Cited by 19 | Viewed by 8104

Abstract

We report the experimental results on a new infrared fiber-optic pyrometer for very localized and high-speed temperature measurements ranging from 170 to 530 °C using low-noise photodetectors and high-gain transimpedance amplifiers with a single gain mode in the whole temperature range. We also [...] Read more.

We report the experimental results on a new infrared fiber-optic pyrometer for very localized and high-speed temperature measurements ranging from 170 to 530 °C using low-noise photodetectors and high-gain transimpedance amplifiers with a single gain mode in the whole temperature range. We also report a shutter based on an optical fiber switch which is optically powered to provide a reference signal in an optical fiber pyrometer measuring from 200 to 550 °C. The tests show the potential of remotely powering via optical means a 300 mW power-hungry optical switch at a distance of 100 m, avoiding any electromagnetic interference close to the measuring point. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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14 pages, 4686 KiB

Open AccessArticle

Overhead Transmission Line Sag Estimation Using a Simple Optomechanical System with Chirped Fiber Bragg Gratings. Part 1: Preliminary Measurements

by Michal Wydra, Piotr Kisala, Damian Harasim and Piotr Kacejko

Sensors 2018, 18(1), 309; https://doi.org/10.3390/s18010309 - 20 Jan 2018

Cited by 63 | Viewed by 7777

Abstract

A method of measuring the power line wire sag using optical sensors that are insensitive to high electromagnetic fields was proposed. The advantage of this technique is that it is a non-invasive measurement of power line wire elongation using a unique optomechanical system. [...] Read more.

A method of measuring the power line wire sag using optical sensors that are insensitive to high electromagnetic fields was proposed. The advantage of this technique is that it is a non-invasive measurement of power line wire elongation using a unique optomechanical system. The proposed method replaces the sag of the power line wire with an extension of the control sample and then an expansion of the attached chirped fiber Bragg grating. This paper presents the results of the first measurements made on real aluminum-conducting steel-reinforced wire, frequently used for power line construction. It has been shown that the proper selection of the CFBG (chirped fiber Bragg grating) transducer and the appropriate choice of optical parameters of such a sensor will allow for high sensitivity of the line wire elongation and sag while reducing the sensitivity to the temperature. It has been shown that with a simple optomechanical system, a non-invasive measurement of the power line wire sag that is insensitive to temperature changes and the influence of high electromagnetic fields can be achieved. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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9 pages, 3306 KiB

Open AccessArticle

Fabry-Perot Interferometric High-Temperature Sensing Up to 1200 °C Based on a Silica Glass Photonic Crystal Fiber

by Haihu Yu, Ying Wang, Jian Ma, Zhou Zheng, Zhuozhao Luo and Yu Zheng

Sensors 2018, 18(1), 273; https://doi.org/10.3390/s18010273 - 18 Jan 2018

Cited by 37 | Viewed by 5843

Abstract

A Fabry-Perot interferometric sensor for temperature measurement was fabricated based on a silica glass solid-core photonic crystal fiber with a central air-bore. By splicing a stub of photonic crystal fiber to a standard single-mode fiber, an intrinsic Fabry-Perot cavity was formed inside the [...] Read more.

A Fabry-Perot interferometric sensor for temperature measurement was fabricated based on a silica glass solid-core photonic crystal fiber with a central air-bore. By splicing a stub of photonic crystal fiber to a standard single-mode fiber, an intrinsic Fabry-Perot cavity was formed inside the photonic crystal fiber. Sensing experiment results show that the sensor can work stably for a consecutive 24 h under temperatures up to 1100 °C, and the short-term operation temperature can reach as high as 1200 °C (<30 min). In the measurement range of 300–1200 °C, the temperature sensitivity of the peak wavelength shift can reach as high as 15.61 pm/°C, with a linearity of 99.76%. The presented interferometric sensor is compact in size and possesses advantages such as an extended working range and high sensitivity, showing promising application prospects. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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7 pages, 3711 KiB

Open AccessArticle

High-Temperature Sensor Based on Fabry-Perot Interferometer in Microfiber Tip

by Zhenshi Chen, Songsong Xiong, Shecheng Gao, Hui Zhang, Lei Wan, Xincheng Huang, Bingsen Huang, Yuanhua Feng, Weiping Liu and Zhaohui Li

Sensors 2018, 18(1), 202; https://doi.org/10.3390/s18010202 - 12 Jan 2018

Cited by 71 | Viewed by 7037

Abstract

A miniaturized tip Fabry-Perot interferometer (tip-FPI) is proposed for high-temperature sensing. It is simply fabricated for the first time by splicing a short length of microfiber (MF) to the cleaved end of a standard single mode fiber (SMF) with precise control of the [...] Read more.

A miniaturized tip Fabry-Perot interferometer (tip-FPI) is proposed for high-temperature sensing. It is simply fabricated for the first time by splicing a short length of microfiber (MF) to the cleaved end of a standard single mode fiber (SMF) with precise control of the relative cross section position. Such a MF acts as a Fabry-Perot (FP) cavity and serves as a tip sensor. A change in temperature modifies the length and refractive index of the FP cavity, and then a corresponding change in the reflected interference spectrum can be observed. High temperatures of up to 1000 °C are measured in the experiments, and a high sensitivity of 13.6 pm/°C is achieved. This compact sensor, with tip diameter and length both of tens of microns, is suitable for localized detection, especially in harsh environments. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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12 pages, 6197 KiB

Open AccessArticle

Optical Fiber Demodulation System with High Performance for Assessing Fretting Damage of Steam Generator Tubes

by Peijian Huang, Ning Wang, Junying Li, Yong Zhu, Jie Zhang and Zhide Xi

Sensors 2018, 18(1), 201; https://doi.org/10.3390/s18010201 - 12 Jan 2018

Cited by 6 | Viewed by 4889

Abstract

In order to access the fretting damage of the steam generator tube (SGT), a fast fiber Fabry-Perot (F-P) non-scanning correlation demodulation system based on a super luminescent light emitting diode (SLED) was performed. By demodulating the light signal coming out from the F-P [...] Read more.

In order to access the fretting damage of the steam generator tube (SGT), a fast fiber Fabry-Perot (F-P) non-scanning correlation demodulation system based on a super luminescent light emitting diode (SLED) was performed. By demodulating the light signal coming out from the F-P force sensor, the radial collision force between the SGT and the tube support plate (TSP) was interrogated. For higher demodulation accuracy, the effects of the center wavelength, bandwidth, and spectrum noise of SLED were discussed in detail. Specially, a piezoelectric ceramic transducer (PZT) modulation method was developed to get rid of the interference of mode coupling induced by different types of fiber optics in the demodulation system. The reflectivity of optical wedge and F-P sensor was optimized. Finally, the demodulation system worked well in a 1:1 steam generator test loop and successfully demodulated a force signal of 32 N with a collision time of 2 ms. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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2796 KiB

Open AccessArticle

Graphene Oxide in Lossy Mode Resonance-Based Optical Fiber Sensors for Ethanol Detection

by Miguel Hernaez, Andrew G. Mayes and Sonia Melendi-Espina

Sensors 2018, 18(1), 58; https://doi.org/10.3390/s18010058 - 27 Dec 2017

Cited by 36 | Viewed by 6293

Abstract

The influence of graphene oxide (GO) over the features of an optical fiber ethanol sensor based on lossy mode resonances (LMR) has been studied in this work. Four different sensors were built with this aim, each comprising a multimode optical fiber core fragment [...] Read more.

The influence of graphene oxide (GO) over the features of an optical fiber ethanol sensor based on lossy mode resonances (LMR) has been studied in this work. Four different sensors were built with this aim, each comprising a multimode optical fiber core fragment coated with a SnO₂ thin film. Layer by layer (LbL) coatings made of 1, 2 and 4 bilayers of polyethyleneimine (PEI) and graphene oxide were deposited onto three of these devices and their behavior as aqueous ethanol sensors was characterized and compared with the sensor without GO. The sensors with GO showed much better performance with a maximum sensitivity enhancement of 176% with respect to the sensor without GO. To our knowledge, this is the first time that GO has been used to make an optical fiber sensor based on LMR. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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5606 KiB

Open AccessArticle

Fiber-Optic Sensor-Based Remote Acoustic Emission Measurement in a 1000 °C Environment

by Fengming Yu and Yoji Okabe

Sensors 2017, 17(12), 2908; https://doi.org/10.3390/s17122908 - 14 Dec 2017

Cited by 37 | Viewed by 7458

Abstract

Recently, the authors have proposed a remote acoustic emission (AE) measurement configuration using a sensitive fiber-optic Bragg grating (FBG) sensor. In the configuration, the FBG sensor was remotely bonded on a plate, and an optical fiber was used as the waveguide to propagate [...] Read more.

Recently, the authors have proposed a remote acoustic emission (AE) measurement configuration using a sensitive fiber-optic Bragg grating (FBG) sensor. In the configuration, the FBG sensor was remotely bonded on a plate, and an optical fiber was used as the waveguide to propagate AE waves from the adhesive point to the sensor. The previous work (Yu et al., Smart Materials and Structures 25 (10), 105,033 (2016)) has clarified the sensing principle behind the special remote measurement system that enables accurate remote sensing of AE signals. Since the silica-glass optical fibers have a high heat-resistance exceeding 1000 °C, this work presents a preliminary high-temperature AE detection method by using the optical fiber-based ultrasonic waveguide to propagate the AE from a high-temperature environment to a room-temperature environment, in which the FBG sensor could function as the receiver of the guided wave. As a result, the novel measurement configuration successfully achieved highly sensitive and stable AE detection in an alumina plate at elevated temperatures in the 100 °C to 1000 °C range. Due to its good performance, this detection method will be potentially useful for the non-destructive testing that can be performed in high-temperature environments to evaluate the microscopic damage in heat-resistant materials. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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3726 KiB

Open AccessArticle

Low Cost Plastic Optical Fiber Pressure Sensor Embedded in Mattress for Vital Signal Monitoring

by Demetrio Sartiano and Salvador Sales

Sensors 2017, 17(12), 2900; https://doi.org/10.3390/s17122900 - 13 Dec 2017

Cited by 45 | Viewed by 8704

Abstract

The aim of this paper is to report the design of a low-cost plastic optical fiber (POF) pressure sensor, embedded in a mattress. We report the design of a multipoint sensor, a cheap alternative to the most common fiber sensors. The sensor is [...] Read more.

The aim of this paper is to report the design of a low-cost plastic optical fiber (POF) pressure sensor, embedded in a mattress. We report the design of a multipoint sensor, a cheap alternative to the most common fiber sensors. The sensor is implemented using Arduino board, standard LEDs for optical communication in POF (λ = 645 nm) and a silicon light sensor. The Super ESKA^® plastic fibers were used to implement the fiber intensity sensor, arranged in a 4 × 4 matrix. During the breathing cycles, the force transmitted from the lungs to the thorax is in the order of tens of Newtons, and the respiration rate is of one breath every 2–5 s (0.2–0.5 Hz). The sensor has a resolution of force applied on a single point of 2.2–4.5%/N on the normalized voltage output, and a bandwidth of 10 Hz, it is then suitable to monitor the respiration movements. Another issue to be addressed is the presence of hysteresis over load cycles. The sensor was loaded cyclically to estimate the drift of the system, and the hysteresis was found to be negligible. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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5147 KiB

Open AccessArticle

Fiber Fabry-Perot Force Sensor with Small Volume and High Performance for Assessing Fretting Damage of Steam Generator Tubes

by Peijian Huang, Ning Wang, Junying Li, Yong Zhu and Jie Zhang

Sensors 2017, 17(12), 2899; https://doi.org/10.3390/s17122899 - 13 Dec 2017

Cited by 5 | Viewed by 4452

Abstract

Measuring the radial collision force between the steam generator tube (SGT) and the tube support plate (TSP) is essential to assess the fretting damage of the SGT. In order to measure the radial collision force, a novel miniaturized force sensor based on fiber [...] Read more.

Measuring the radial collision force between the steam generator tube (SGT) and the tube support plate (TSP) is essential to assess the fretting damage of the SGT. In order to measure the radial collision force, a novel miniaturized force sensor based on fiber Fabry-Perot (F-P) was designed, and the principle and characteristics of the sensor were analyzed in detail. Then, the F-P force sensor was successfully fabricated and calibrated, and the overall dimensions of the encapsulated fiber F-P sensor were 17 mm × 5 mm × 3 mm (L × W × H). The sensor works well in humid, high pressure (10 MPa), high temperature (350 °C), and vibration (40 kHz) environments. Finally, the F-P force sensors were installed in a 1:1 steam generator test loop, and the radial collision force signals between the SGT and the TSP were obtained. The experiments indicated that the F-P sensor with small volume and high performance could help in assessing the fretting damage of the steam generator tubes. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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1196 KiB

Open AccessArticle

Two Interrogated FBG Spectral Linewidth for Strain Sensing through Correlation

by Shih-Hsiang Hsu, Kuo-Wei Chuang, Ci-Syu Chen, Ching-Yu Lin and Che-Chang Chang

Sensors 2017, 17(12), 2837; https://doi.org/10.3390/s17122837 - 7 Dec 2017

Viewed by 4011

Abstract

The spectral linewidth from two cross-correlated fiber Bragg gratings (FBGs) are interrogated and characterized using a delayed self-homodyne method for fiber strain sensing. This approach employs a common higher frequency resolution instead of wavelength. A sensitivity and resolution of 166 MHz/με and 50 [...] Read more.

The spectral linewidth from two cross-correlated fiber Bragg gratings (FBGs) are interrogated and characterized using a delayed self-homodyne method for fiber strain sensing. This approach employs a common higher frequency resolution instead of wavelength. A sensitivity and resolution of 166 MHz/με and 50 nε were demonstrated from 4 GHz spectral linewidth characterization on the electric spectrum analyzer. A 10 nε higher resolution can be expected through random noise analyses when the spectral linewidth from two FBG correlations is reduced to 1 GHz. Moreover, the FBG spectrum is broadened during strain and experimentally shows a 0.44 pm/με sensitivity, which is mainly caused by the photo elastic effect from the fiber grating period stretch. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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6346 KiB

Open AccessArticle

All-Fiber Laser Curvature Sensor Using an In-Fiber Modal Interferometer Based on a Double Clad Fiber and a Multimode Fiber Structure

by Ricardo I. Álvarez-Tamayo, Manuel Durán-Sánchez, Patricia Prieto-Cortés, Guillermo Salceda-Delgado, Arturo A. Castillo-Guzmán, Romeo Selvas-Aguilar, Baldemar Ibarra-Escamilla and Evgeny A. Kuzin

Sensors 2017, 17(12), 2744; https://doi.org/10.3390/s17122744 - 28 Nov 2017

Cited by 20 | Viewed by 5111

Abstract

An all-fiber curvature laser sensor by using a novel modal interference in-fiber structure is proposed and experimentally demonstrated. The in-fiber device, fabricated by fusion splicing of multimode fiber and double-clad fiber segments, is used as wavelength filter as well as the sensing element. [...] Read more.

An all-fiber curvature laser sensor by using a novel modal interference in-fiber structure is proposed and experimentally demonstrated. The in-fiber device, fabricated by fusion splicing of multimode fiber and double-clad fiber segments, is used as wavelength filter as well as the sensing element. By including a multimode fiber in an ordinary modal interference structure based on a double-clad fiber, the fringe visibility of the filter transmission spectrum is significantly increased. By using the modal interferometer as a curvature sensitive wavelength filter within a ring cavity erbium-doped fiber laser, the spectral quality factor Q is considerably increased. The results demonstrate the reliability of the proposed curvature laser sensor with advantages of robustness, ease of fabrication, low cost, repeatability on the fabrication process and simple operation. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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13616 KiB

Open AccessArticle

Assembled Cantilever Fiber Touch Trigger Probe for Three-Dimensional Measurement of Microstructures

by Limin Zou, He Ni, Peng Zhang and Xuemei Ding

Sensors 2017, 17(11), 2652; https://doi.org/10.3390/s17112652 - 20 Nov 2017

Cited by 5 | Viewed by 5977

Abstract

In this paper, an assembled cantilever fiber touch trigger probe was developed for three-dimensional measurements of clear microstructures. The probe consists of a shaft assembled vertically to an optical fiber cantilever and a probing sphere located at the free end of the shaft. [...] Read more.

In this paper, an assembled cantilever fiber touch trigger probe was developed for three-dimensional measurements of clear microstructures. The probe consists of a shaft assembled vertically to an optical fiber cantilever and a probing sphere located at the free end of the shaft. The laser is emitted from the free end of the fiber cantilever and converges on the photosensitive surface of the camera through the lens. The position shift of the light spot centroid was used to detect the performance of the optical fiber cantilever, which changed dramatically when the probing sphere touched the objects being measured. Experimental results indicated that the sensing system has sensitivities of 3.32 pixels/μm, 1.35 pixels/μm, and 7.38 pixels/μm in the x, y, and z directions, respectively, and resolutions of 10 nm, 30 nm, and 5 nm were achieved in the x, y, and z, respectively. An experiment on micro slit measurement was performed to verify the high aspect ratio measurement capability of the assembled cantilever fiber (ACF) probe and to calibrate the effective two-point diameter of the probing sphere. The two-point probe sphere diameter was found to be 174.634 μm with a standard uncertainly of 0.045 μm. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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1866 KiB

Open AccessArticle

Optical Spring Effect in Micro-Bubble Resonators and Its Application for the Effective Mass Measurement of Optomechanical Resonant Mode

by Zhenmin Chen, Xiang Wu, Liying Liu and Lei Xu

Sensors 2017, 17(10), 2256; https://doi.org/10.3390/s17102256 - 30 Sep 2017

Cited by 8 | Viewed by 5593

Abstract

In this work, we present a novel approach for obtaining the effective mass of mechanical vibration mode in micro-bubble resonators (MBRs). To be specific, the effective mass is deduced from the measurement of optical spring effect (OSE) in MBRs. This approach is demonstrated [...] Read more.

In this work, we present a novel approach for obtaining the effective mass of mechanical vibration mode in micro-bubble resonators (MBRs). To be specific, the effective mass is deduced from the measurement of optical spring effect (OSE) in MBRs. This approach is demonstrated and applied to analyze the effective mass of hollow MBRs and liquid-filled MBRs, respectively. It is found that the liquid-filled MBRs has significantly stronger OSE and a less effective mass than hollow MBRs, both of the extraordinary behaviors can be beneficial for applications such as mass sensing. Larger OSE from higher order harmonics of the mechanical modes is also observed. Our work paves a way towards the developing of OSE-based high sensitive mass sensor in MBRs. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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3926 KiB

Open AccessArticle

A Hot-Polymer Fiber Fabry–Perot Interferometer Anemometer for Sensing Airflow

by Cheng-Ling Lee, Kai-Wen Liu, Shi-Hong Luo, Meng-Shan Wu and Chao-Tsung Ma

Sensors 2017, 17(9), 2015; https://doi.org/10.3390/s17092015 - 2 Sep 2017

Cited by 38 | Viewed by 5707

Abstract

This work proposes the first hot-polymer fiber Fabry–Perot interferometer (HPFFPI) anemometer for sensing airflow. The proposed HPFFPI is based on a single-mode fiber (SMF) endface that is attached to a UV-cured polymer to form an ultracompact fiber Fabry–Perot microcavity. The proposed polymer microcavity [...] Read more.

This work proposes the first hot-polymer fiber Fabry–Perot interferometer (HPFFPI) anemometer for sensing airflow. The proposed HPFFPI is based on a single-mode fiber (SMF) endface that is attached to a UV-cured polymer to form an ultracompact fiber Fabry–Perot microcavity. The proposed polymer microcavity was heated using a low-cost chip resistor with a controllable dc driving power to achieve a desired polymer’s steady-state temperature (T) that exceeds the T of the surrounding environment. The polymer is highly sensitive to variations of T with high repeatability. When the hot polymer was cooled by the measured flowing air, the wavelength fringes of its optical spectra shifted. The HPFFPI anemometers have been experimentally evaluated for different cavity lengths and heating power values. Experimental results demonstrate that the proposed HPFFPI responses well in terms of airflow measurement. A high sensitivity of 1.139 nm/(m/s) and a good resolution of 0.0088 m/s over the 0~2.54 m/s range of airflow were achieved with a cavity length of 10 μm and a heating power of 0.402 W. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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1861 KiB

Open AccessArticle

Differential Phononic Crystal Sensor: Towards a Temperature Compensation Mechanism for Field Applications Development

by Simón Villa-Arango, David Betancur Sánchez, Róbinson Torres, Panayiotis Kyriacou and Ralf Lucklum

Sensors 2017, 17(9), 1960; https://doi.org/10.3390/s17091960 - 25 Aug 2017

Cited by 41 | Viewed by 6240

Abstract

Phononic crystals are resonant structures with great potential to be implemented in applications as liquid sensors. The use of the symmetry reduction technique allows introducing relevant transmission features inside bandgaps by creating defect modes in a periodic regular structure. These features can be [...] Read more.

Phononic crystals are resonant structures with great potential to be implemented in applications as liquid sensors. The use of the symmetry reduction technique allows introducing relevant transmission features inside bandgaps by creating defect modes in a periodic regular structure. These features can be used as measures to quantify changes in the speed of sound of liquid samples that could be related to the concentration of analytes or the presence of pathogens among other interesting applications. In order to be able to implement this new technology in more challenging applications, such as biomedical applications, it is necessary to have a very precise and accurate measurement. Changes in temperature greatly affect the speed of sound of the liquid samples, causing errors in the measurements. This article presents a phononic crystal sensor that, by introducing additional defect modes, can carry out differential measurements as a temperature compensation mechanism. Theoretical studies using the transmission line model and analytes at various temperatures show that the proposed temperature compensation mechanism enhances the performance of the sensor in a significant way. This temperature compensation strategy could also be implemented in crystals with different topologies. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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2767 KiB

Open AccessArticle

Radiation-Induced Attenuation of Perfluorinated Polymer Optical Fibers for Radiation Monitoring

by Pavol Stajanca and Katerina Krebber

Sensors 2017, 17(9), 1959; https://doi.org/10.3390/s17091959 - 25 Aug 2017

Cited by 41 | Viewed by 5247

Abstract

Due to some of their unique properties, optical fiber dosimeters are attractive and extensively researched devices in several radiation-related areas. This work evaluates the performance and potential of commercial perfluorinated polymer optical fibers (PF-POFs) for radiation monitoring applications. Gamma radiation-induced attenuation (RIA) of [...] Read more.

Due to some of their unique properties, optical fiber dosimeters are attractive and extensively researched devices in several radiation-related areas. This work evaluates the performance and potential of commercial perfluorinated polymer optical fibers (PF-POFs) for radiation monitoring applications. Gamma radiation-induced attenuation (RIA) of two commercial PF-POFs is evaluated in the VIS spectral region. Influence of a dose rate and temperature on RIA measurement is investigated, along with defect stability and measurement repeatability. Co-extruded PF-POFs are identified as more suitable for radiation monitoring applications due to lower dose-rate dependence. With co-extruded PF-POF, RIA measurement holds potential for highly-sensitive radiation monitoring with good reproducibility. The results show that operation in the blue part of the spectrum provides most favorable performance in terms of the largest nominal radiation sensitivity, lower temperature, and dose-rate dependence as well as higher defect stability. We demonstrate for the first time to our knowledge, that PF-POFs can be used for distributed detection of radiation with doses down to tens of Grays. The off-the-shelf, user-friendly PF-POF could be of interest as a cheap, disposable sensor for various applications, especially of a more qualitative nature. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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9073 KiB

Open AccessArticle

Curvature and Temperature Measurement Based on a Few-Mode PCF Formed M-Z-I and an Embedded FBG

by Hui Liu, Hangzhou Yang, Xueguang Qiao, Yongqiang Wang, Xiaochong Liu, Yen-Sian Lee, Kok-Sing Lim and Harith Ahmad

Sensors 2017, 17(8), 1725; https://doi.org/10.3390/s17081725 - 27 Jul 2017

Cited by 28 | Viewed by 5003

Abstract

We have experimentally demonstrated an optical fiber Mach-Zehnder interferometer (MZI) structure formed by a few-mode photonic crystal fiber (PCF) for curvature measurement and inscribed a fiber Bragg grating (FBG) in the PCF for the purpose of simultaneously measuring temperature. The structure consists of [...] Read more.

We have experimentally demonstrated an optical fiber Mach-Zehnder interferometer (MZI) structure formed by a few-mode photonic crystal fiber (PCF) for curvature measurement and inscribed a fiber Bragg grating (FBG) in the PCF for the purpose of simultaneously measuring temperature. The structure consists of a PCF sandwiched between two multi-mode fibers (MMFs). Bending experimental results show that the proposed sensor has a sensitivity of −1.03 nm/m⁻¹ at a curvature range from 10 m⁻¹ to 22.4 m⁻¹, and the curvature sensitivity of the embedded FBG was −0.003 nm/m⁻¹. Temperature response experimental results showed that the MZI’s wavelength, λ_a, has a sensitivity of 60.3 pm/°C, and the FBG’s Bragg wavelength, λ_b, has sensitivity of 9.2 pm/°C in the temperature range of 8 to 100 °C. As such, it can be used for simultaneous measurement of curvature and temperature over ranges of 10 m⁻¹ to 22.4 m⁻¹ and 8 °C to 100 °C, respectively. The results show that the embedded FBG can be a good indicator to compensate the varying ambient temperature during a curvature measurement. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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Review

Jump to: Research

31 pages, 81980 KiB

Open AccessReview

Distributed Optical Fiber Sensors Based on Optical Frequency Domain Reflectometry: A review

by Zhenyang Ding, Chenhuan Wang, Kun Liu, Junfeng Jiang, Di Yang, Guanyi Pan, Zelin Pu and Tiegen Liu

Sensors 2018, 18(4), 1072; https://doi.org/10.3390/s18041072 - 3 Apr 2018

Cited by 256 | Viewed by 20381

Abstract

Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) [...] Read more.

Distributed optical fiber sensors (DOFS) offer unprecedented features, the most unique one of which is the ability of monitoring variations of the physical and chemical parameters with spatial continuity along the fiber. Among all these distributed sensing techniques, optical frequency domain reflectometry (OFDR) has been given tremendous attention because of its high spatial resolution and large dynamic range. In addition, DOFS based on OFDR have been used to sense many parameters. In this review, we will survey the key technologies for improving sensing range, spatial resolution and sensing performance in DOFS based on OFDR. We also introduce the sensing mechanisms and the applications of DOFS based on OFDR including strain, stress, vibration, temperature, 3D shape, flow, refractive index, magnetic field, radiation, gas and so on. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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25 pages, 3246 KiB

Open AccessReview

Optical Fiber Sensors Based on Fiber Ring Laser Demodulation Technology

by Wen-Ge Xie, Ya-Nan Zhang, Peng-Zhao Wang and Jian-Zhang Wang

Sensors 2018, 18(2), 505; https://doi.org/10.3390/s18020505 - 8 Feb 2018

Cited by 35 | Viewed by 7375

Abstract

A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory [...] Read more.

A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory background of the sensors has been discussed. Secondly, four different types of sensors are described and compared, which includes Mach–Zehnder interferometer (MZI) typed sensors, Fabry–Perot interferometer (FPI) typed sensors, Sagnac typed sensors, and fiber Bragg grating (FBG) typed sensors. Typical studies and main properties of each type of sensors are presented. Thirdly, a comparison of different types of sensors are made. Finally, the existing problems and future research directions are pointed out and analyzed. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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26 pages, 8896 KiB

Open AccessFeature PaperReview

A Review of Microfiber-Based Temperature Sensors

by Wanvisa Talataisong, Rand Ismaeel and Gilberto Brambilla

Sensors 2018, 18(2), 461; https://doi.org/10.3390/s18020461 - 4 Feb 2018

Cited by 61 | Viewed by 8783

Abstract

Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness. [...] Read more.

Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness. Additionally, they can perform in-situ measurements remotely and in harsh environments. This paper presents an overview of optical microfibers, with a focus on their applications in temperature sensing. This review broadly divides microfiber-based temperature sensors into two categories: resonant and non-resonant microfiber sensors. While the former includes microfiber loop, knot and coil resonators, the latter comprises sensors based on functionally coated/doped microfibers, microfiber couplers, optical gratings and interferometers. In the conclusions, a summary of reported performances is presented. Full article

(This article belongs to the Special Issue Optical Fiber Sensors 2017)

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